The present invention relates to a mobile diagnosis device comprised of an ECG unit to record an ECG signal, with the ECG unit being connected or connectible to two or more ECG electrodes to dissipate electrical signals from a patient's body, and comprised of a pulsoximetry unit for simultaneous recording of a volume pulse signal, with the pulsoximetry unit comprising at least one light source and at least one light sensor for optical measurement of blood perfusion in the vascular system of a patient's body tissue, and comprised of a program-controlled evaluation unit to evaluate the ECG signal and the volume pulse signal.
Cardio-vascular diseases are the main cause of death in nearly all industrialized countries, as is well known. A special rank is taken by arteriosclerosis, i.e. the pathological stenosis of blood vessels. Approx. 50% of patients suffering from ateriosclerosis are also affected by coronary heart disease. On account of the clearly recognizable progression of cardio-vascular diseases and the restricted therapeutical possibilities in the late stages of these diseases, it is intended to strive for the earliest possible diagnosis. To this effect it is necessary to realize and evaluate complex correlations in a cardio-vascular system. Both the heart and the blood vessels must be evaluated equally in their functional status to permit early diagnosis. A healthy vascular system can offset minor heart insufficiencies for years, as is well known, while a vascular system already affected by arteriosclerosis advances circulatory decompensation.
The ECG (electrocardiogram) might be the most frequently applied examination modality for diagnosis of cardio-vascular diseases. By means of an ECG device, electrical signals are dissipated with two or more ECG electrodes from the body of a patient to be examined. The ECG thus obtained reflects the bioelectrical voltages that occur during excitation spread and regression at the heart. The ECG contains numerous parameters that can be diagnostically evaluated. At the moment when the heart muscle contracts during a heart beat, the ECG shows an evident peak which is also designated as R peak. Furthermore, the ECG contains the so-called P wave which precedes the R peak. The R peak, in turn, is followed by what is called a T wave. The minimum levels in the ECG immediately before and immediately after the R peak are designated by Q and S, respectively. Those parameters of interest for cardio-vascular diagnostics are the duration of the P wave as well as the amplitude of the P wave, the duration of the PQ interval, the duration of the QRS complex, the duration of the QT interval as well as the amplitude of the T wave. Both from the absolute values of the a.m. parameters and from the ratios of these parameters, it is possible to draw conclusions on the health status of the cardiovascular system.
Capturing and recording of peripheral cardio-vascular parameters is feasible by what is called plethysmography. In plethysmography, blood-flow conditioned volume fluctuations of a peripheral blood vessel are measured. Nowadays, the NIRP method (near infrared photo plethysmography) has won its way. The diagnostic modalities applied therein are briefly called pulsoximeters. Such pulsoximeters typically comprise two light sources which radiate red and/or infrared light of a different wavelength into the human body tissue of a patient. The light is scattered in a patient's body tissue and partly absorbed. The scattered light is detected by means of a light sensor in form of an appropriate photocell. Commercial pulsoximeters, on the one hand, typically use light in a wavelength range of 660 nm. Within this range, the light absorption of oxyhemoglobin and deoxyhemoglobin differs substantially. The intensity of the scattered light detected by means of the light sensor varies accordingly, dependent upon how strongly the examined body tissue is supplied with blood rich in oxygen or poor in oxygen, respectively. On the other hand, light in a wavelength range of 810 nm is commonly used. This light wavelength lies in what is called near infrared spectral range. The light absorption of oxyhemoglobin and deoxyhemoglobin within this spectral range is essentially equal. Prior art pulsoximeters are capable of generating a volume pulse signal that reflects the blood volume which is variable during a heart beat and which passed by the micro-vessel system captured by the pulsoximeter. When different light wavelengths are employed in the afore-mentioned spectral ranges, it is possible to draw conclusions from the different light absorption to evaluate the oxygen content of blood (oxygen saturation). Commonly applied pulsoximeters are either employed at the patient's finger tip or at the lobe of the ear. The volume pulse signal is then generated from the blood perfusion of the micro-vessel system in these regions of the body tissue.
A prior art disclosed in U.S. Pat. No. 4,960,126 is an ECG-synchronized pulsoximeter. The prior art equipment is comprised of an ECG unit and a pulsoximetry unit. With the prior art diagnosis device, the ECG unit is utilized to determine the heart beat cycle by detection of R peaks in the ECG signal. The duration of the heart beat cycle is then taken as the basis in determining the oxygen saturation by means of the pulsoximetry unit. Thereby, it is intended to improve signal averaging and reduce motion-induced artefacts. On the whole, a more reliable determination of the value of oxygen saturation of blood is achieved thereby as compared with conventional pulsoximeters.
Known combined ECG and pulsoximetry devices allow for determining a plurality of cardiovascular parameters. Based upon these data, a practicing doctor can make a comprehensive cardio-vascular diagnosis, to be true. But prior art devices have a drawback in that they do not allow for an automatic establishment of a preliminary diagnosis of imminent or already existing cardio-vascular diseases. For this reason, prior art devices cannot be readily employed by patients for auto-diagnosis either.
Against this background, it is the object of the present invention to provide a diagnosis device that allows for an (at least coarse) status and trend diagnosis of the cardio-vascular system. This device is intended to be capable of indicating to a patient an early auto-diagnosis of a cardio-vascular disease without posing excessive demands on a patient in terms of evaluating a plurality of diagnostic parameters.